mfunc

Meadhbh's FUNCtional programming library in javascript

This is a simple module that works with node & browsers to add simple functional programming primitives. These are no better than ones provided by other languages, they're just in a format I like to use.

This module adds:

Function.prototype._$partial( args ) - this function returns a function which pre-applies some number of arguments. Here's an example cribbed from http://dailyjs.com/2012/09/14/functional-programming/ :

function add(x,y) { return x+y; };
var add_three = plus_two.$_partial(3);
console.log( add_three(4) ); // this should print the number 7

Function.prototype._$compose( function ) - this function returns a function which executes the base function (the thing you do the _$compose() on) on the output of the function you pass as a parameter to _$compose(). Example:

function add2( x ) { return 2+x; }
function mult2( x ) { return 2*x; };
var add_then_mult = mult2._$compose( add2 );
console.log( add_then_mult( 7 ) ); // should print the number 18

Function.prototype._$flip() - returns a function whose arguments are reversed.

function div(x,y) { return x/y; }
var recip = div._$flip();
console.log( div( 10, 5 ) ); // should print the number 2
console.log( recip( 10, 5 ) ); // should print the number 0.5

Function.prototype._$negate() returns a function whose value is the logical negation of the original.

function isTwo( x ) { return 2 == x; }
var isNotTwo = isTwo._$negate();
console.log( isTwo( 1 ) ); // should print false
console.log( isTwo( 2 ) ); // should print true
console.log( isNotTwo( 1 ) ); // should print true
console.log( IsNotTwo( 2 ) ); // should print false

Array.prototype._$each(function) and Object.prototype._$each(function) Iterates through array calling the function passed for each value passing the element and the index as parameters. 'this' is set as the array (or object).

Array.prototype._$map(function) and Object.prototype._$map(function) Iterates through each element of the array (or object), creating a new array (or object) whose elements are the contents of the original array passed through the function provided.

Object.prototype._$fold( function, base ) Iterates through the object's members combining the output of the value returned from the function provided with the base value specified.